1. Field of the Invention
The present invention relates to an air conditioning apparatus having inlets for taking in indoor air at the front portion and upper portion of the indoor unit.
2. Description of the Related Art
Generally, the indoor unit of an air conditioning apparatus has an inlet at its front portion and an outlet at its lower portion. An air passage is formed from the inlet to the outlet, and an indoor heat exchanger and an indoor fan are provided along the air passage. Hence, when the indoor fan is operated, indoor air is taken in through the inlet, passes through the indoor heat exchanger, and is discharged into the room through the outlet.
An example of such an air conditioning apparatus is an apparatus described in Published Unexamined Japanese Utility Model Application No. 59-172921. In this air conditioning apparatus, an inlet is formed at an front portion of an indoor unit, and an outlet is formed at the lower portion of the indoor unit. An air passage is formed from the inlet to the outlet, and an indoor heat exchanger and an indoor fan are provided along the air passage. An inlet grill is provided to the inlet. The inlet grill can be manually opened/closed. When the air conditioning apparatus is not to be used for a long period of time, the inlet grill is closed, so that dust will not enter the indoor unit.
Another example of the indoor unit is an indoor unit having inlets at its front and upper portions, respectively. In this case, an indoor heat exchanger is provided to oppose the respective inlets. That is, although the size of the indoor unit is decreased, a sufficiently large heat exchange area of the indoor heat exchanger is assured.
However, in this indoor unit having the inlets at its front and upper portions, respectively, the sound caused by the hissing indoor fan and the sound caused by the refrigerant flowing in the indoor heat exchanger leak to the ceiling of the room through the upper inlet and are reflected by the ceiling, which are regarded as noise by the person in the room. This noise gives discomfort to the person in the room.
In an air conditioning apparatus having a heat pump type refrigerating cycle, a cooling operation can be executed by operating the indoor heat exchanger as an evaporator, and a heating operation can be executed by operating the indoor heat exchanger as a condenser.
In some air conditioning apparatuses each having the heat pump type refrigerating cycle, a reheater is provided downstream the indoor heat exchanger, so that the apparatus has a function of a dehumidifying operation in addition to the functions of the cooling and heating operations. In the dehumidifying operation, the indoor heat exchanger serves as an evaporator, and the reheater is operated, so that air cooled and dehumidified by the indoor heat exchanger is heated by the reheater and discharged into the room. That is, dehumidified air whose temperature is not excessively low is discharged into the room.
There are a plurality of types of dehumidifying operations, e.g., a mode of a dehumidifying operation on the cooling side wherein the temperature of air discharged into the room is lower than the indoor temperature, an isothermal dehumidifying operation mode wherein air discharged into the room is maintained at substantially the same temperature as that of the indoor temperature, and a mode of a dehumidifying operation on the heating side wherein the temperature of air discharged into the room is higher than the indoor temperature.
In an air conditioning apparatus using an electric heater as the reheater, in the mode of the dehumidifying operation on the cooling side, the capability of the compressor is set to a predetermined value or more, and the cooling capacity of the indoor heat exchanger is increased. In the isothermal dehumidifying operation mode, the capability of the compressor is set to a predetermined value or less, and the cooling capacity of the indoor heat exchanger is decreased.
It must be noted that, in the air conditioning apparatus described above which has the inlets at the plurality of portions of the indoor unit to increase the heat exchange area in the indoor heat exchanger, even when the isothermal dehumidifying operation mode is set, since the heat exchange quantity of the indoor heat exchanger is large, the temperature of air discharged into the room is largely decreased, and the obtained air conditioning result is the same as that obtained in the mode of the dehumidifying operation on the cooling side. As a result, the person in the room feels chilly.
In order to solve this inconvenience, the capacity of the electric heater serving as the reheater may be increased. However, in the recent trend of the size reduction of the indoor unit, the electric heater and other components are close to each other. Thus, when the capacity of the electric heater is excessively increased, heat generated by the electric heater adversely affects other components.
As an alternative way of solving the above inconvenience, the capability of the compressor may be decreased as low as possible. When, however, the capability of the compressor is excessively decreased, the evaporative temperature of the refrigerant in the indoor heat exchanger is increased, and in an extreme case, the temperature of the discharged indoor air cannot be maintained at a dew point temperature or less, and the dehumidifying function is disabled.
In order to solve this problem, the capability of the compressor may be decreased as low as possible, and at the same time the blowing air quantity of the indoor fan may be decreased. That is, the heat exchange efficiency of the indoor heat exchanger is degraded to suppress an increase in evaporative temperature. In this case, however, since the blowing air quantity of the indoor fan must be extremely decreased, the air conditioning efficiency becomes poor, and a sufficiently high dehumidifying effect cannot be obtained.